Legumes Become Newest Sustainable Crop

A new study examined the mineral micronutrient content of four types of grain legumes: field peas, lentils, chickpeas, and common bean.

Jun 10, 2014

A recent study published in Crop Science examined the mineral micronutrient content of crops grown in the province of Saskatchewan, Canada. The study was conducted jointly by the University of Saskatchewan and North Dakota State University. The researchers examined four types of grain legumes (pulses)—field peas, lentils, chickpeas, and common bean. Although these legumes have up to twice the micronutrients as cereals, according to Tom Warkentin, professor of plant breeding at the University of Saskatchewan, they are not cultivated on the same scale as cereals in most countries. This means that grain legume crops are often overlooked as potentially valuable sources of micronutrients.

The study found that genetic characteristics and environmental conditions—such as soil properties and local climate—can affect the micronutrient content of grain legumes. The researchers measured micronutrient levels by a technique known as atomic absorption spectrometry. According to Warkentin, “In the case of selenium, we found that environmental conditions are more important than genotype.”

“A 100-gram (3 ½-ounce) serving of any one of the four grain legume crops studied provided a substantial portion of the recommended daily allowance (RDA) of iron, zinc, selenium, magnesium, manganese, copper, and nickel,” said Warkentin.

The serving size was based on the dry weight of the grain legumes. Warkentin adds that lentils were the best source of iron, while chickpeas and common bean were higher in magnesium. Calcium was the only key micronutrient that these crops lacked.

Most of the crops studied were high in selenium, with chickpeas and lentils being the best sources. Selenium is an important but often overlooked micronutrient. Selenium deficiency can lead to diseases that weaken heart muscles and cause breakdown of cartilage. It can also give rise to hypothyroidism, since selenium is a required chemical in the production of thyroid hormone.

Since grain legume crops don’t require nitrogen-based fertilizers, which are derived from fossil fuels, they are very sustainable.

“Increased production and consumption of grain legume crops should be encouraged by agriculturalists and dietitians around the world.” Warkentin said, “Grain legume crops are highly nutritious. In addition to the micronutrients described in this research, they also contain 20-25 percent protein, 45-50 percent slowly digestible starch, soluble and insoluble fiber, and are low in fat.”